If you're having trouble getting Linux to run on that 8-bit processor with 32KB of memory don't despair, there are open-source alternatives. FreeRTOS [1] is an open source real time kernel that has been ported to a number of microprocessors. The website [2] lists ports to over 40 different processor/compiler combinations.

FreeRTOS [3] supports both co-routines and tasks and numerous forms of IPC. All tasks (and co-routines) run in a single memory space so they are more akin to threads in Linux.

The source consists of 3 or 4 (depending on features used) C source code files plus header files. Porting to a new architecture requires modification to only one of the C files and one of the header files. Depending on the compiler and the compiler options, the basic kernel object code can be reduced to less than 4KB.

FreeRTOS [4] is actively developed and both community and paid support are available. There is also a version available that has been certified for use in safety critical applications. Version 5.0 of FreeRTOS [5] was released in April.

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Mitch Frazier is the System Administrator at Linux Journal.